Electrocautery method and apparatus

ABSTRACT

An electrode structure and a mechanism for automated or user-selected operation or compensation of the electrodes, for example to determine tissue coverage and/or prevent arcing between bottom electrodes during electrocautery is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/062,516 filed Apr. 4, 2008, which is a divisional of U.S. patentapplication Ser. No. 11/671,891, filed Feb. 6, 2007 (Attorney DocketNo.: ARAG0016), which is a continuation-in-part of U.S. applicationsSer. No. 11/382,635 filed May 10, 2006 (Attorney Docket No.: ARAG0002)and Ser. No. 11/371,988 filed Mar. 8, 2006 (Attorney Docket No.:ARAG003), and claims the benefit thereof in accordance with 35 USC 120.U.S. application Ser. No. 11/382,635 filed May 10, 2006 in turn, claimsthe benefit of provisional applications 60/725,720 filed on Oct. 11,2005 (Attorney Docket No. ARAG0001PR) and 60/680,937 filed on May 12,2005 (Attorney Docket No. ARAG005PR). The entireties of the foregoingapplications are incorporated herein by this reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to tissue cauterization. More particularly, theinvention concerns an electrocautery system with various electrodes anda mechanism for automated or user-selected operation or compensation ofthe electrodes.

2. Description of the Related Art

Various physiological conditions call for tissue and organ removal. Amajor concern in all tissue removal procedures is hemostasis, that is,cessation of bleeding. All blood vessels supplying an organ or a tissuesegment to be removed have to be sealed, either by suturing orcauterization, to inhibit bleeding when the tissue is removed. Forexample, when the uterus is removed in a hysterectomy, bleeding must beinhibited in the cervical neck, which must be resected along the certainvessels that supply blood to the uterus. Similarly, blood vessels withinthe liver must be individually sealed when a portion of the liver isresected in connection with removal of a tumor or for other purposes.Achieving hemostasis is necessary in open surgical procedures as well asminimally invasive surgical procedures. In minimally invasive surgicalprocedures, sealing of blood vessels can be especially time consumingand problematic because there is limited access via a cannula and othersmall passages.

Achieving hemostasis is particularly important in limited accessprocedures, where the organ or other tissue must be morcellated prior toremoval. Most organs are too large to be removed intact through acannula or other limited access passage, thus requiring that the tissuebe morcellated, e.g. cut, ground, or otherwise broken into smallerpieces, prior to removal.

In addition to the foregoing examples, there exist a variety of otherelectrosurgical instruments to seal and divide living tissue sheets,such as arteries, veins, lymphatics, nerves, adipose, ligaments, andother soft tissue structures. A number of known systems apply radiofrequency (RF) energy to necrose bodily tissue. Indeed, some of theseprovide significant advances and enjoy widespread use today.Nevertheless, the inventors have sought to identify and correctshortcomings of previous approaches, and to research possibleimprovements, even when the known approaches are adequate.

In this respect, one problem recognized by the inventors concerns thesmall size of today's electrode structures. In particular, manyelectrosurgical instrument manufacturers limit the total length andsurface area of electrodes to improve the likelihood of completelycovering the electrodes with tissue. This small electrodes strategyresults in the surgeon having to seal and divide multiple times to sealand divide long tissue sheets adequately. Such time consuming processesare also detrimental to patients, increasing anesthetic time andpotentially increasing the risk of injury to surrounding structures, asthe delivery of energy and division of tissue is repeated again andagain.

The consequences of partial electrode coverage can be significant. Thiscondition can cause electrical arcing, tissue charring, and inadequatetissue sealing. Mechanical, e.g. blade, or electrosurgical division oftissue is performed immediately following tissue sealing, and thedivision of inadequately sealed tissue can pose a risk to the patientbecause unsealed vessels may hemorrhage. Arcing presents its own set ofproblems. If electrocautery electrodes generate an arc between them,instead of passing RF energy through targeted tissue, the tissue failsto undergo the intended electrocautery. Furthermore, depending upon thepath of the arc, this might damage non-targeted tissue. Another problemis that adjacent electrodes in a multiple electrode system may generateelectrical cross-talk or generate excessive thermal effect in thetransition zone between two adjacent electrodes that fire sequentially.Previous designs prevented this by imposing a mechanical standoff forthe jaws that the electrodes were fastened onto. However, this standoffprevented very thin tissue from making contact with the opposingelectrodes, preventing an optimal electrical seal in these regions.These standoffs, if too shallow, can also result in arcing betweenelectrodes.

At typical radiofrequency energy (RF) frequencies in the 300 kHz to 10MHz range, tissue impedance is largely resistive. Prior to tissuedesiccation, initial impedances can vary greatly depending on the tissuetype and location, vascularity, etc. Thus, to ascertain the adequacy oftissue electrode coverage based solely on local impedance is impreciseand impractical. A feasible and dependable methodology for determiningelectrode coverage by tissue would allow for the development ofelectrodes of greater length and surface area for use in the safe andrapid sealing and division of tissue sheets during surgical procedures.It would therefore be advantageous to provide a methodology fordetermining the area of tissue coverage of one or more electrodes.

SUMMARY

An electrode structure and a mechanism for automated or user-selectedoperation or compensation of the electrodes, for example to determinetissue coverage and/or prevent arcing between bottom electrodes duringelectrocautery is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the components and interconnections of anelectrocautery system according to the invention;

FIG. 2 is a combination block and schematic diagram illustrating anelectrocautery device with a first embodiment of compensating circuitryaccording to the invention;

FIG. 3 is a combination block and schematic diagram illustrating anelectrocautery device with a second embodiment of compensating circuitryaccording to this invention;

FIG. 4 is a combination block and schematic diagram illustrating anelectrocautery device with a third embodiment of compensating circuitryaccording to the invention;

FIG. 5 is a combination block and schematic diagram illustrating anelectrocautery device with circuitry for selectively firing electrodesaccording to the invention; and

FIG. 6 is a block diagram showing an electrode having a dielectriccoating according to the invention.

DETAILED DESCRIPTION

In view of the problems of conventional technology that the inventorshave recognized (as discussed above), the inventors have sought toimprove the ability of a user to control electrocautery electrodes aftersaid electrode have been inserted into the body. Further areas of theirfocus include improving the efficiency of transferring power toelectrode structures, and improving the accuracy of measurements takenfrom the electrode structure in situ. One benefit of implementing theseimprovements is the ability to use larger electrode surfaces, with theadvantageous consequences discussed above.

FIG. 1 illustrates one embodiment of electrocautery system 100. Thesystem 100 includes an electrode structure 102 that is electricallydriven by a power, electrode selector, and compensator module 108. Themodule 108 is operated in accordance with user input conveyed via one ormore user interfaces 110.

As explained below in greater detail, certain components of the system100 may be implemented with digital data processing features. These maybe implemented in various forms.

Some examples include a general purpose processor, digital signalprocessor (DSP), application specific integrated circuit (ASIC), fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g. a combination ofa DSP and a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

As a more specific example, a digital data processing includes aprocessor, such as a microprocessor, personal computer, workstation,controller, microcontroller, state machine, or other processing machine,coupled to digital data storage. In the present example, the storageincludes a fast-access storage, as well as nonvolatile storage. Thefast-access storage may be used, for example, to store the programminginstructions executed by the processor. Storage may be implemented byvarious devices. Many alternatives are possible. For instance, one ofthe components may be eliminated. Furthermore, the storage may beprovided on-board the processor, or even provided externally to theapparatus.

The apparatus also includes an input/output, such as a connector, line,bus, cable, buffer, electromagnetic link, antenna, IR port, transducer,network, modem, or other means for the processor to exchange data withother hardware external to the apparatus.

As mentioned above, various instances of digital data storage may beused, for example, to provide storage used by the system 100 (FIG. 1),to embody the storage, etc. Depending upon its application, this digitaldata storage may be used for various functions, such as storing data, orto store machine-readable instructions. These instructions maythemselves aid in carrying out various processing functions, or they mayserve to install a software program upon a computer, where such softwareprogram is then executable to perform other functions related to thisdisclosure.

An exemplary storage medium is coupled to a processor so the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.In another example, the processor and the storage medium may reside inan ASIC or other integrated circuit.

In contrast to storage media that contain machine-executableinstructions (as described above), a different embodiment uses logiccircuitry to implement processing data processing features of thesystem.

Depending upon the particular requirements of the application in theareas of speed, expense, tooling costs, and the like, this logic may beimplemented by constructing an application-specific integrated circuit(ASIC) having thousands of tiny integrated transistors. Such an ASIC maybe implemented with CMOS, TTL, VLSI, or another suitable construction.Other alternatives include a digital signal processing chip (DSP),discrete circuitry (such as resistors, capacitors, diodes, inductors,and transistors), field programmable gate array (FPGA), programmablelogic array (PLA), programmable logic device (PLD), and the like.

Electrode Structure 102

Referring to FIG. 1, the electrode structure 102 includes first andsecond electrode surfaces 103-104. The electrode surface 104 is formedby a group of electrodes, such as individual electrodes 104 a, 104 b,etc. In one instance, the electrodes may be substantially contiguous.The electrode surface 103, in one instance, includes a single electrode,as illustrated. In another instance, the surface 103 includes multipleelectrodes, of the same or different number than the electrodes 104.

In one embodiment the electrode surfaces 103-104 are arranged to provideelectrical power to a targeted tissue area using opposed, bipolarelectrodes. The use of opposed, bipolar electrodes is advantageousbecause it concentrates energy flux between the electrodes and limitsthe effect on adjacent tissue that is not confined within the opposedelectrodes.

In one case, the electrode structures 103-104 may have generally similargeometries to contact tissue in a symmetric fashion. Alternatively, theelectrode structures 103-104 may have dissimilar geometries. Forexample, one electrode structure may comprise a probe for insertion intoa natural body orifice with the other electrode structure beingstructured to engage an exterior tissue surface apart from the bodyorifice. In some instances, more than two electrode structures may beemployed, but at least two electrode structures, or separate regions ofa single structure, are energized with opposite polarity to apply RFenergy to the targeted tissue. In some instances, the electrodestructures may be different regions formed as part of a single supportstructure, e.g. a single elastic tube or shell which may be placed overan organ or other tissue mass and which has two or more electrodesurfaces formed thereon.

The different electrode surfaces are isolated from each other when highfrequency energy of the same or opposite polarity is applied to them. Instill other instances, a single electrode structure may have a pluralityof electrically conductive or active regions, where the electricallyconductive regions may be energized with the same or an oppositepolarity.

In some instances, it may be desirable to provide additional structureor components on the electrode structures to enhance or increase theeffective electrical contact area between the electrode structure andthe tissue. In particular, the electrode structures may includetissue-penetrating elements to enhance electrical contact i.e. reduceelectrical impedance between the electrode and the tissue and increasethe total surface contact area between the electrode and the tissue.Exemplary tissue-penetrating elements include needles, pins,protrusions, channels, or the like. A particular example includes pinshaving sharpened distal tips so that they can penetrate through thetissue surface and into the underlying tissue mass. The pins may havedepths in the range from 1 mm to 5 cm, or from 3 mm to 1 cm. Thediameters of the pins range from 0.1 mm to 5 mm, or from 0.5 mm to 3 mm.In one instance, the pins are evenly distributed over the tissue-contactarea of an electrode structure, with a pin density in the range from 0.1pin/cm² to 10 pin/cm², or from 0.5 pin/cm² to 5 pin/cm². Whentissue-penetrating elements are used, they may be dispersed in a generaluniform matter over the electrically active area of the electrodestructure. The pins or other tissue-penetrating elements may be providedin addition to an electrically conductive conformable or rigid electrodesurface, but in some instances the pins may provide the totalelectrically conductive or active area of an electrode structure.

In one example, the electrodes comprise a plurality of differentelectrically conductive regions, where the regions may be electricallyisolated from each other or may be electrically coupled to each other.Single electrode structures may include three, four, five, and as manyas ten or more discrete electrically conductive regions thereon. Suchelectrically conductive regions may be defined by electricallyinsulating regions or structure between them.

One example of a multiple-electrode surface 104 is a plurality ofelectrically conductive strips that are separated by a gap which may bean air gap, a plastic member or other insulator. The gap is preferablyless than 0.5 mm. In addition, multiple tissue-penetrating pins may bedisposed along the length of each electrically conductive strips. Theelectrically conductive strips may be energized in an alternatingpolarity configuration. Most simply, opposing strips are connected toopposite polls on a single power supply. Electrical connections may berearranged, however, to power the strips in virtually any pattern.Moreover, it is also possible to isolate different regions of each stripelectrically to permit powering those regions at different polarities;or to set the electrodes to the same polarity but with various sequencesof firing pattern that can include firing every electrode, firingspecific electrode, or firing multiple electrodes simultaneously.

Although shown as flat plates, the electrode structure 102 may beimplemented in a variety of different shapes without departing from thescope of the invention. For instance, the electrode structures 103-104may be generally curved to facilitate placement over a tubular bodystructure or tissue mass. In one case, electrode configurations arespecifically configured to have a geometry intended to engage aparticular organ or tissue geometry. In other cases, the electrodeconfigurations are conformable so that they can be engaged against andconform to widely differing tissue surfaces. In this regard, electrodestrips may be constructed from such material as, for example,conformable meshes, permitting the electrode structures to be flattenedout or to assume a wide variety of other configurations. Additionally,the insulating structures may also be formed from a flexible orconformable material, permitting further reconfiguration of theelectrode structures. The structure 102 may be implemented according inany one, or a combination, of known shapes configurations, which arefamiliar to the ordinarily skilled artisan. Some exemplary shapesinclude opposing jaws, cylinder, probe, flat pads, etc. In this regard,the electrodes may be configured in any manner suitable for engaging atissue surface.

Thus, the electrodes can be rigid, flexible, elastic, inelastic(non-distensible), planar, non-planar, or the like, and may optionallyemploy tissue-penetrating elements to enhance electrical contact betweenthe electrode structure and the tissue, as well as to increase theelectrode area. Electrode configurations may be conformable so that theycan be engaged against and conform to widely differing tissue surfaces,or they are specifically configured to have a geometry intended toengage a particular organ or tissue geometry. In both instances, theelectrode structures may further be provided with tissue-penetratingelements.

Optionally, electrode structures may include both a conductive surfaceand a non-conductive surface. In some embodiments this is accomplishedby leaving one surface as an exposed metallic face, while the othersurface of the electrode is covered or insulated with, for example, adielectric material. In the case of rigid electrodes, the insulation canbe laminated, coated, or otherwise applied directly to the opposedsurface. In the case of flexible and elastic electrodes, the insulatinglayer is flexible so that it can be expanded and contracted togetherwith the electrode without loss or removal. In some cases, a separate,expandable sheet of material covers the face for which insulation isdesired. In some embodiments, all electrode surfaces may be coated witha dielectric material.

In one embodiment, the electrically active regions of the electrodestructures have an area ranging from one to fifty cm² or larger. Furtherdetails and examples of electrode structures are explained in the U.S.patent applications as identified incorporated herein by referenceabove.

Power Supply 106

The power supply 106 includes one or multiple power supplies. Basically,the power supply 106 generates high frequency, such as RF, power forapplication to targeted tissue through one or more electrically activeregions of the electrode structure 102. As described below, the durationand magnitude of power cauterizes or necroses tissue between theelectrode surfaces 103-104.

Exemplary frequency bands include 100 kHz to 10 MHz or 200 kHz to 750kHz. Power levels depend on the surface area and volume of tissue beingtreated, with some examples including a range from 10 W to 500 W, or 25W to 250 W, or 50 W to 200 W. Power may be applied at a level of from 1W/cm² to 500 W/cm², or 10 W/cm² to 100 W/cm², for example.

The power supply 106 may be implemented using various conventionalgeneral purpose electrosurgical power supplies. The power supply 106 mayemploy sinusoidal or non-sinusoidal wave forms and may operate withfixed or controlled power levels. Suitable power supplies are availablefrom commercial suppliers.

In one embodiment, the power supply provides a constant output power,with variable voltage and current, where power output varies based uponload. Thus, if the system sees a very high impedance load, the voltageis maintained at a reasonable level to avoid arcing. With tissueelectrocautery, impedance ranges from two ohms to 1000 ohms, forexample. By applying constant power, the power supply 106 can providesignificant current at low impedance to achieve initial desiccation whenthe tissue is first being cauterized and, as cauterization proceeds, toapply higher voltage to complete the tissue sealing process. Thus, thepower supply 106 can provide larger current and smaller voltage at thebeginning of the cauterization process and a higher voltage and lowercurrent at the sealing phase of the process. Control of such powergenerator is based, at least in part, on the system 100 monitoringpower.

In one embodiment, the power supply 106 includes a mechanism for settingthe desired power. This setting may occur by real-time control, pre-setselection by a user, default settings, selection of predeterminedprofile, etc. In one embodiment, pulse width modulation is used inconnection with a flyback transformer. The system charges a primary ofthe flyback transformer and produces a regulated output. The secondarymay be regulated, for example, to 15 volts at a desired number ofamperes to produce the desired power output. Based upon the period, asdetermined by the width of the pulse which charges the primary, thepower curve is determined. Thus, the invention establishes a certainlevel of power in the primary of the flyback transformer and the samelevel of power is provided by the secondary without regard to impedanceof the load, i.e. the tissue.

The power supply 106 may include digital data processing equipment, suchas mentioned above. This optional equipment, if implemented, is used toestablish and control features and operation of the power supply 106.

As illustrated, the power supply 106 is a source of power for multipleelectrodes of the structure 102. Accordingly, the power supply 106, orthe module 108, provides multiple output channels, each of which isindependently adjustable. In this embodiment, the system 100 includes aconductive supply path of multiple conductors 108 c to provide power tothe electrodes, and a return path 108 b for providing a ground pathand/or feedback to the power supply or vice versa, depending on thedirection of current flow.

In a more particular embodiment, the module 108 has multiple outputs 108c routed to the individual electrodes by a digital data processor of themodule 108. These multiple outputs are independently operated by theprocessor and readily modulated and assignable. Thus, the processor mayassign an output to any one or more of the electrode elements at acertain point in operation of a cauterization cycle, and dynamicallyreassign them other points of time. For example, if the power sourcewere a four channel power source and the electro-surgical device hadsixteen electrodes, then each channel may support four electrodes inelectro-surgical device. However, this arrangement may be varied so thatsome channels support more electrodes than others.

User Interface 110

The user interface 110 comprises one or more devices for a human toexchange information with the module 108, including the power supply106. There may be a common user interface, or separate user interfacesfor each component 106, 108. The user interface may be implemented invarious ways, with the following serving as some examples. As forhuman-to-machine flow, some examples of the interface 110 includebuttons, dials, switches, keyboards, remote control console, or othermechanical devices. Other examples include pointing devices such as amouse, trackball, etc. Still other examples include digitizing pads,touch screens, voice input, or any other example suitable for thepurposes described herein. As for the machine-to-human exchange, theinterface 110 may employ a video monitor, display screen, LEDs,mechanical indicators, audio system, or other example suitable for thepurposes described herein.

User input is conveyed from the interface to the module 108 via the link108 a.

Sensors

The system 100 may also include various sensors attached to variouscomponents of the system 100. The sensors, which are not shown in FIG. 1to avoid cluttering the diagram, may be attached to components such asthe electrodes 103-104, subparts of the module 108, equipment of thepower supply 106, and the like. Examples of these sensors includedevices for sensing voltage, current, impedance, phase angle betweenapplied voltage and current, temperature, energy, frequency, etc. Moreparticular, some of these devices include voltmeters, analog-to-digitalconverters, thermistors, transducers, ammeters, etc.

Module 108

As shown above, the module 108 includes one or more power supplies 106.Aside from this function, module 108 may be implemented to perform someor all of automated or user-selected operation or compensation of theelectrodes in the manner shown below. According to one aspect, themodule 108 may be used to target a specific region of tissue, or thecontrol firing order of electrodes, by selectively limiting powerapplication to electrodes whose selection is predetermined,machine-selected, or user-selected. According to another aspect, themodule 108 may introduce impedance into the electrode circuitry toprovide a predetermined, machine-selected, or user-selected impedancematching or compensation.

According to one optional aspect of the module 108, the module 108 maytarget a specific region of tissue by selectively limiting powerapplication to electrodes whose selection is predetermined,machine-selected, or user-selected. In this regard, the module 108 has avariety of outputs 108 b-108 c individually coupled to each of theelectrodes 103-104. As one example, the outputs 108 b-108 c may comprisewires, cables, busses, or other electrical conductors. In theillustrated example, there are multiple conductors 108 c leading to themultiple electrodes 104 a, 104 b, etc.

The module 108 applies voltage from the power supply 106 across thefirst and second electrode surfaces 103-104, such that the voltage isapplied exclusively to selected ones of the electrodes. These electrodesmay be selected according to user input from the interface 110, selectedby a machine-implemented analysis, and/or selected by a default state.In this regard, the module 108 may include a switching network ofelectrical and/or mechanical switches, relays, or other mechanism toprovide power to selected ones of the electrodes. As shown, the powersupply 106 is integrated into the module 108, and computer controlselectively activates selected output conductors.

Whether by independent switching network or computer regulatedactivation of output conductors, the module 108 activates electrodesaccording to input from user interface 110, or input from a machine suchas a digital data processing device as discussed above. Depending uponthe nature of the application, such controlled application of power toelectrodes may be performed in accordance with a machine-selectedcriteria or analysis, default state, or user input.

FIG. 5 illustrates a typical application of one example of aprocessor-controlled switching network, shown in context of two powersupplies, electrode structures, and a targeted tissue region. In thisexample, the electrode surfaces are configured as follows. The electrodesurfaces are substantially parallel during performance ofelectrocautery, each electrode of one surface is aligned with itscounterpart in the other electrode surface. In this example, there aretwo electrodes from the upper surface corresponding to each electrode ofthe lower surface.

Significantly, the module 108 selectively limits power application tocertain electrodes, to target a specific region of tissue. Electrodesmay be selected for a different end, as well. Namely, the module 108 maymonitor or control the selection of electrodes to prevent firing ofadjacent electrodes of the same electrode surface concurrently orsequentially. Ensuring that electrode firing occurs in this spaced-apartfashion prevents unintentional arcing between electrodes and improvesthe effectiveness of electrocautery. In one embodiment, the controlledfiring order is implemented by computer control, and particularly, by adigital data processing component of the module 108. As an alternativeto computer control, mechanical means may be used, such as anelectromechanical distributor or other device.

In another embodiment, the module 108 may introduce impedance into theelectrode circuitry to provide predetermined, machine-selected, fixed,or user-selected impedance matching or compensation. In other words, themodule 108 contains a mechanism to electrically introduce impedance intoa circuit containing the power supply, the outputs 108 b-108 c, and theelectrodes 103-104.

More particularly, the module 108 includes capacitors, inductors, and/orother impedance elements that can be adjusted or selectively introducedto control the amount of impedance in the circuit containing the powersupply and electrodes 103-104. These impedance elements may comprisediscrete elements, integrated circuit features, or other constructssuitable for the purposes described herein. The module 108 establishesthis impedance matching or compensation according to directions from auser, machine-implemented analysis, and/or default setting.

One example of an adjustable impedance is an adjustable inductor thatmay comprise any known inductance, such as a coil of conducting materialwrapped around an adjustable ferromagnetic core or discrete inductors.In this example, the overall inductance is selectively increased byclosing a switch that may be activated manually, mechanically,electrically, or by any means suitable to the purposes of thisdisclosure, for example, via the user interface 110.

FIG. 2 illustrates an electrode arrangement having an inductance inseries with each electrode of an upper electrode surface (asillustrated). FIG. 3 shows a different example, including an inductancein series with each electrode of the lower electrode surface (asillustrated). In a different example still, FIG. 4 contains “T” typenetwork where a capacitor is placed in series with each electrode of theupper electrode surface. Additionally, a different inductor is placed inparallel with each pair of electrodes that are designed to be activatedtogether. The examples of FIGS. 2-4 may employ impedance elements thatare fixed, adjustable, or a combination of fixed and adjustable.Furthermore, in connection with the electrodes having a dielectriccoating on their surface, a nearly limitless number of additionalcircuitry configurations for impedance matching and/or compensation willbe apparent to ordinarily skilled artisans having the benefit of thisdisclosure.

In addition to the arrangement for introducing impedance into theelectrode circuits, another consideration is the value of such impedanceelements. In one example, the impedance is selected to achieve maximumpower transfer and to make accurate power measurements. In this regard,the impedance is chosen to maintain an impedance match between the RFgenerator, namely, the power supply 106, and the tissue. Impedancematching is achieved when the phase-angle between applied voltage andcurrent is zero. Namely, additional inductance is increased tocompensate for the increased capacitive reactance. in one example, thisis carried out with a continuously variable inductor, with a finiterange and nearly infinite resolution. Such an inductor can be adjustedto a near zero phase. In a different example, impedance matching iscarried out by using discrete inductive elements in an appropriatearrangement, such as shown in FIGS. 2-4, to find the least possiblephase angle, though this may not be exactly zero.

Having described the structural features of the invention, theoperational aspects of the invention will be described. The steps of anymethod, process, or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by hardware, human-performed steps, or acombination of these.

A sequence for performing an electrocautery procedure uses anelectrocautery system that includes an electrode structure and amechanism for automated or user-selected operation or compensation ofthe electrodes. For ease of explanation, but without any intendedlimitation, this example is described in the specific context of thesystem 100 of FIG. 1.

In a first step, different parameters for operating the system 100 areselected. In one example, one or more human users select theseparameters and convey them to the system 100 via the user interface 110.In a different example, the parameters for operating the system 100 areselected by digital data processing equipment aboard the module 108. Inthis case, the parameters are set according to user input, defaultvalues, measurements gathered by the various sensors installed in thesystem 102, programming of the module 108, etc.

Without any intended limitation, the following are some non-exclusiveexamples of parameters that may be selected in the first step:

-   -   (1) Identity of individual electrodes to be activated e.g., FIG.        5 in order to focus energy of the electrodes 103-104 on a        specific region of tissue.    -   (2) Firing order of electrodes.    -   (3) Assessment or measurement of magnitude of impedance, e.g.        FIGS. 2-4, to be used in compensating and/or impedance matching        between the power supply 106 and electrodes 103-104.    -   (4) Parameters of electrical power to be applied in        electrocautery, such as magnitude, frequency, phase, or other        characteristics of voltage, current, power, etc.    -   (5) Any other parameter by which the operation of the system 100        can be varied.

In a next step appropriately trained personnel apply the electrodes103-104 to a targeted tissue region to be electrocauterized. The mannerof applying the electrodes 103-104, varies according to the constructionof the electrodes 103-104, the nature of the targeted body part, theprocedure to be performed, and other such factors. There may becircumstances where both electrode structures 103-104 are used withinthe body, and other embodiments where one electrode is inserted into thebody and the other electrode used externally, i.e. bipolar or monopolarapplications, as is know in the art.

In a specific example of this next step, there are multiple electrodesof one surface, such as 104, corresponding to one electrode of the othersurface, such as 103. Optionally, personnel arrange the first and secondelectrode surfaces 103-104 so that the electrode surfaces aresubstantially parallel, and each one of the second electrodes is alignedwith its corresponding first electrodes, although alignment ispreferably obtained during manufacture of the device. FIGS. 2-5 showexamples of the final arrangement.

In a further step, directions are given to begin electrocautery. Thisoccurs by user input submitted via the interface 110. For example, auser may press a start button, utter a start command, press a footpedal, trip a lever, or perform other action. In a different example,electronically occurs upon expiration of a user-initiated timer.

In a still further step, the system 100 responds to the start commandand electrocautery is conducted. Here, the system 100 directs bipolar RFpower at target tissue regions defined by spaced-apart placement of theelectrode structures 103-104. The use of opposed, bipolar electrodesconcentrates energy between the electrodes and limits the effect onadjacent tissue that is not confined within the opposed electrodes. Inpractice, power may be applied for a time sufficient to raise the tissuetemperature in the tissue mass being treated to above a threshold levelrequired for cauterization or necrosis, such as 60-80° C., or evenhigher.

More specifically, electrocautery is conducted according to theconfiguration set. For instance, the power supply 106 operates accordingto the power settings established. Moreover, the module 108 acts toinvoke individual ones of the electrodes according to the electrodecombination selected. In other words, the module 108 applies voltagefrom the power supply 106 across the first and second electrode surfaces103-104, such that voltage is applied exclusively to the electrodesselected in. In the case of computer control, this is achieved by themodule 108 selectively applying power to the selected electrodes.

As a further enhancement to the use of selected electrodes, theelectrodes may be activated using a selected firing order. In thisexample, the module 108 applies voltage from the power supply 106 acrossthe first and second electrode surfaces 103-104, such that voltage isapplied to one or more of the first electrodes 102 and one or more ofthe second electrodes 103 at any one time, and the module 108 preventsfiring of adjacent electrodes of the same electrode surface concurrentlyor sequentially. The module 108 may further implement a predetermined oruser-selected firing order.

For example, one way of preventing interaction, either thermal orelectrical, between two or more multiple electrodes in an RF device withmultiple electrodes is to alter the firing sequence of electrodes sothat adjacent electrodes are never sequentially charged. For example,instead of sequential firing a four electrode system, where theelectrodes are sequentially numbered 1, 2, 3, 4, the invention firesthem in an order such as 3, 1, 4, 2, 4, 2, 4, 1, 3, 1, 3, etc. so thatadjacent electrodes are not fired sequentially. Firing times may bedifferent for each electrode to balance the energy delivered in such asequence where some electrodes fire more frequently than others. Thisprevents cross-talk during the transmission from one electrode toanother as well as cumulative effects of sequential heat build-up in thetransition area between the two electrodes. Additionally, roundedelectrodes can minimize the edge effect that occurs between electrodesand at any transition surface.

Additionally, if one electrode surface or both opposing surface ofconductive, typically metal, electrodes are coated with dielectric,non-conductive materials, RF energy may still be transmitted throughtissue between them via capacitive coupling. FIG. 6 is a block diagramshowing an electrode having a dielectric coating according to theinvention. However, due to the non-conductive nature of the surfacecoating the electrode surfaces does not create a short circuit ifbrought into close proximity or contact. In this way, if a portion of anelectrode pair only partially captures tissue, i.e. there is a small, 5mm air gap between a portion of the electrodes, the RF energy stillpasses through the tissue, as opposed to going around the tissue andflowing directly between the close proximity electrodes. This isespecially important late in the sealing cycle as the tissue impedancerises. When the tissue impedance is high the energy seeks alternatepathways of lower resistance, such as between exposed electrodesections. These dielectric layers can be thin coats of polymers, such asTeflon, metal oxides, such as titanium, tungsten, or tantalum orceramics. To obtain adequate capacitance these layers may be in themicron range of thickness.

In an alternative embodiment, a variety of different tissuecauterization patterns can be achieved with the system 100 byselectively energizing different ones of the electrode surfaces orregions. By selectively energizing two adjacent electrodes, whileleaving all other electrodes non-energized, a limited tissue region iscauterized. In contrast, by energizing other multiple electrodesurfaces, a larger region is cauterized. Slightly different patterns areachieved depending on the precise pattern of electrode surface polarity.In other embodiments, the electrode surfaces can be energized in analternating pattern of polarity to produce a tissue cauterizationpattern. Different patterns may also be used to produce somewhatdifferent patterns of cauterized tissue.

A different approach for selected firing is employed to prevent localareas of high impedance from impacting the overall system impedancealong the entire electrode, and thus potentially reducing the poweroutput of the entire system as voltage reaches its maximal capacity.Here, electrodes are activated to prevent one area that has already beenwell sealed and has thus reached high impedance value from affectingother regions in which the tissue is not yet sealed, and is thus at alower impedance. Optionally, the module 108 may employ unique power andenergy delivery profiles for each electrode or electrode pair, based onthe properties of the tissue in a specific electrode location/position.

The performance of electrocautery employs the selected impedancecompensation and/or matching selected. As a result, power delivered fromthe power supply 106 is delivered to the targeted tissue region withless electrical loss.

The system 100 may further sense and automatically adjust conjugatematching impedance. In response, the module 108 adjusts the impedanceapplied to the conductive path containing the electrode surfaces 103-104and power supply 106. Alternatively, the sensors may provide raw data tothe module 108, which analyzes whether and how to adjust impedance. In adifferent instance, the module 108 may adjust impedance responsive todirection or data from the sensors. This can be carried out by changingthe frequency of RF energy delivered by the power supply 106. Forexample, in one embodiment the module 108 senses whether or not tissueis present at each electrode at the beginning of a cauterization cycleby measuring any of impedance, pressure, or any combination of theseand/or other parameters. If tissue is not present at any electrode, thensuch electrode pair is idle; the module 108 deactivates firing of thiselectrode, and/or provides a warning to an operator via the userinterface 110. The module 108 may also provide a status indicator foreach electrode pair that indicates whether the sealing cycle is activeor completed with regard to each electrode pair. In this embodiment,each electrode pair may include a mode status indicator, such as an LEDfor example, that indicates any of an idle, active, or completecondition, once a cauterization cycle is commenced.

The invention also addresses the problem of determining the area oftissue coverage of one or more electrodes through the use of dielectriccoated electrode surfaces (See FIG. 6). With a suitable RF generator andwith electrode surfaces coated with a dielectric coating, determinationof tissue coverage may be obtained by measuring phase-angle of RFvoltage and current. Because a dielectric coating essentially forms acapacitive coupling to tissue, for a given dielectric materialthickness, the capacitance is a function of the area of coverage.

The basic formula for a capacitor is:

C=ε ₀ε_(r) A/d

Expressed in Farads, where ε₀ is the permittivity of free-space(8.854E-12), ε_(r), is the relative permittivity of the dielectric, A/dis the ratio of the area and the dielectric thickness.

At a given frequency, the reactance is expressed as

Xc=1/ωC

where ω is 2*Pi*Frequency.

A suitable RF generator is required to insert a conjugate impedanceinductance in this case to cancel out the capacitive reactance with afully covered electrode and to measure the phase-angle of RF voltage andcurrent. When an electrode is only partially covered, the capacitancechanges i.e. becomes smaller, because the effective area is smaller. Asa result, the reactance and, ultimately, the phase-angle of RF voltageand current change. While the magnitude of change is affected in part bythe tissue resistance, it is believed that this methodology allows thegreatest degree of determination of electrode coverage by tissue.

A further advantage of such a methodology may signal the RF generator'scontrol algorithm to change frequency, e.g. increase, with smallersurface areas, thus maintaining maximum power transfer while minimizingchances for electrical arcing and tissue charring. Potential electricalarcing and tissue charring conditions may be detected rapidly by rapidchanges in phase and/or impedance and by appreciating that electrodeswhich are only partially covered by tissue may be used to signal the RFgenerator control algorithm to shorten or change treatment parameters.

To achieve maximum power transfer and to make accurate powermeasurements, it is desirable to maintain an impedance match between theRF generator and the tissue. Impedance matching is achieved when thephase-angle is zero. Several methodologies may be used to attainnear-zero phase. One such methodology uses additional reactive elementse.g. greater inductance, to compensate for the increased capacitivereactance. This approach can be achieved in two different ways:

-   -   (1) Via the insertion of a continuously variable inductor with a        finite range and nearly infinite resolution, such an inductor        can be adjusted to a near zero phase; or    -   (2) Via the insertion of discrete elements, e.g. inductors to        find the lowest phase, though this may not be near-zero phase.

In both cases, electromechanical devices are required within the RFgenerator.

Another methodology of achieving maximum power-transfer, e.g. zerophase, is by changing the RF frequency. Given that the reactance isfrequency dependent, this methodology allows the RF generator tocompensate for phase discrepancy by electronically changing frequency.This may not require any mechanical devices such as relays, servos, etc.Further, the RF generator can change frequency during operation ratherthan first interrupting RF power to change elements. Thus, this may bethe most desirable methodology.

Although the invention is described herein with reference to thepreferred embodiment, one skilled in the art will readily appreciatethat other applications may be substituted for those set forth hereinwithout departing from the spirit and scope of the present invention.Accordingly, the invention should only be limited by the Claims includedbelow.

1. An electrocautery apparatus, comprising: at least one firstelectrode; at least one second electrode; a power supply having at leastone adjustable output channel for application of high frequency power totargeted tissue via selective coupling of said high frequency power tosaid at least one first electrode and to said at least one secondelectrode; at least one sensor for sensing at least one parametercomprising any of voltage, current, impedance, phase angle betweenapplied voltage and current, temperature, energy, and frequency and forproducing an output representative of a value or rate of change of saidat least one parameter; means, responsive to said at least one sensor,for controlling at least one aspect of said high frequency powerprovided by said power supply; and means for selectively applying saidhigh frequency power provided by said power supply between said at leastone first electrode and said at least one second electrode; wherein saidhigh frequency power provided by said power supply cauterizes ornecroses tissue between surfaces of said at least one first electrodeand said at least one second electrode.
 2. The apparatus of claim 1,wherein said power supply is adjustable by any of real-time control,pre-set selection by a user, default settings, or selection of apredetermined profile.
 3. The apparatus of claim 1, further comprising:means for determining the area of tissue coverage of said at least onefirst electrode and said at least one second electrode by measuringphase-angle of RF voltage and current.
 4. The apparatus of claim 1, saidpower generating high frequency power in frequency bands comprising anyof 100 kHz to 10 MHz or 200 kHz to 750 kHz.
 5. The apparatus of claim 1,said power generating high frequency power at power levels comprisingany of 10 W to 500 W, or 25 W to 250 W, or 50 W to 200 W.
 6. Theapparatus of claim 1, said power supplying high frequency power to saidat least one first electrode and said at least one second electrode atpower levels comprising any of 1 W/cm² to 500 W/cm² or 10 W/cm² to 100W/cm².
 7. The apparatus of claim 1, said sensor comprising any of: avoltmeter, analog-to-digital converter, thermistor, transducer, orammeter.
 8. The apparatus of claim 1, said means for controlling saidhigh frequency power provided by said power supply further comprising:means for selecting impedance to maintain an impedance match betweensaid power supply and said tissue to achieve maximum power transfer andto make accurate power measurements; wherein impedance matching isachieved when the phase-angle between applied voltage and current is ator near zero.
 9. The apparatus of claim 8, said means for controllingsaid high frequency power provided by said power supply furthercomprising: an inductive element that is adjustable to a near zero phaseangle to increase inductance and compensate for increased capacitivereactance.
 10. The apparatus of claim 1, said power supply comprisingadjustment means for any of: assessing or measuring magnitude ofimpedance to be used in compensating and/or impedance matching betweensaid power supply and said at least first electrode and said at leastone second electrode; and establishing at least one parameter ofelectrical power to be applied in electrocautery, said parameterscomprising voltage, current, impedance, phase angle between appliedvoltage and current, temperature, energy, frequency, and/or rate ofchange of said at least one parameter.
 11. The apparatus of claim 1,wherein said at least one sensor is constructed to provide raw data tosaid means for controlling said high frequency power provided by saidpower supply, said means for controlling said high frequency powerprovided by said power supply comprising means for analyzing whether andhow to adjust impedance by changing the frequency of RF energy deliveredby said power supply.
 12. The apparatus of claim 1, said means forcontrolling said high frequency power provided by said power supply, inconjunction with said at least one sensor, further comprising: means fordetermining whether or not tissue is present at each electrode at thebeginning of a cauterization cycle by measuring any of voltage, current,impedance, phase angle between applied voltage and current, temperature,energy, frequency, and/or rate of change of said at least one parameter;wherein, if tissue is not present at any electrode, then said electrodeis idle; wherein said means for controlling said high frequency powerprovided by said power supply comprises means that deactivates firing ofsaid idle electrode, and/or provides a warning to an operator via a userinterface.
 13. The apparatus of claim 11, said means for controllingsaid high frequency power provided by said power supply furthercomprising: a status indicator for each electrode that indicates any ofan idle, active, or complete condition, once a cauterization cycle iscommenced with regard to each said electrode.
 14. The apparatus of claim1, wherein said at least one second electrode comprises at least onereturn electrode.
 15. The apparatus of claim 2, said power supplycomprising: an RF generator selectively operable by said means forselectively applying a voltage from the power supply to insert aconjugate impedance in the form of an inductance to cancel outcapacitive reactance with a fully covered electrode and to permitmeasurement of phase-angle of RF voltage and current; wherein when anelectrode is only partially covered, capacitance changes; and wherein,as a result, reactance and phase-angle of RF voltage and current change.16. The apparatus of claim 2, said means for selectively applying avoltage from the power supply further comprising: an RF generatorcontrol algorithm for changing RF generator frequency upon detection ofsmaller electrode surface areas to maintain maximum power transfer whileminimizing electrical arcing and suboptimal and/or excessive energydelivery.
 17. The apparatus of claim 1, said means for selectivelyapplying a voltage from the power supply further comprising: means fordetecting electrical arcing and preventing suboptimal and/or excessiveenergy delivery by determining rapid changes in phase and/or impedance.18. The apparatus of claim 3, means for detecting electrical arcing andpreventing suboptimal and/or excessive energy delivery furthercomprising: means for using electrodes which are only partially coveredby tissue to signal said RF generator control algorithm to shorten orchange treatment parameters.
 19. The apparatus of claim 15, said meansfor selectively applying a voltage from the power supply furthercomprising: means for maintaining an impedance match between said RFgenerator and tissue; wherein impedance matching is achieved when aphase-angle is about zero.
 20. The apparatus of claim 19, said means formaintaining an impedance match between said RF generator and tissuefurther comprising: one or more reactive elements which compensate forincreased capacitive reactance.
 21. The apparatus of claim 20, saidmeans for maintaining an impedance match between said RF generator andtissue further comprising any of: means for insertion of a continuouslyvariable inductor with a finite range and nearly infinite resolution,wherein said inductor adjustable to a near zero phase; means forinsertion of discrete elements to find a lowest phase; and means forchanging the frequency of said RF generator, wherein said RF generatorcompensates for phase discrepancy by electronically changing frequency.22. The apparatus of claim 1, said power supply further comprising apulse width modulation mechanism for establishing a desired poweroutput.
 23. An electrocautery method, comprising the steps of: providingat least one first electrode; providing at least one second electrode;selectively applying high frequency power to targeted tissue by couplinghigh frequency power to said at least one first electrode and to said atleast one second electrode from a power supply; sensing at least oneparameter comprising any of voltage, current, impedance, phase anglebetween applied voltage and current, temperature, energy, and frequencyand for producing an output representative of a value or rate of changeof said at least one parameter; and responsive to said outputrepresentative of a value or rate of change of said at least oneparameter, controlling at least one aspect of said high frequency powerprovided by said power supply; wherein said high frequency powerprovided by said power supply cauterizes or necroses tissue betweensurfaces of said first electrode array and said at least one secondelectrode.